Molded propeller



Nov. 30, 1943. R. w. 'DEVORE ETAL MOLDED PROPELLER Filed May 9, 1959 jfipezz/ors: I 205622 $.leaore {224.5622 W Patented Nov. 30, 1943UNITEDYSTATES PATENT OFFICE MOLDED PRDPELLER Robert W- Devore and Ben H.Young, Chicago, Ill.

Application May 9, 1939, Serial No. 272,596 2 Claims. (01. 170-159) Theinvention relates to propellers, particularly a propeller of the screwtype, and has as a general object to provide a propeller of new andimproved construction.

There has long been an unfulfilled demand for a sturdy yet economicallymanufactured propeller, for fans and air circulators, particularly,whose hub and also whose blades are composed of some material that willnot corrode and will not deteriorate as a result of the chemicalreaction of the fluids, vapors, and the like, to which the propeller issubjected in use, depending upon the place of use for the deviceutilizing the propeller. Attempts have been made to fulfill this demandby constructing the blades of the propeller of some pressed,non-corrosive'material and securing the same to a metallic hub or bymaking both the hub and the blades of some pressed, noncorrosivematerial and securing the same together. However, such attempts have allbeen unsuccessful because corrosion and deterioration of all of theparts was not avoided, or because of structural defects, or because thecost of manufacture has been prohibitive.

It is a primary object of the invention, therefore, to provide apropeller fulfilling this demand, and, more particularly, to provide apropeller composed of a moldable plastic composition and having its huband blades molded integrally to form a unitary structure. I

While a plastic composition propeller molded with the hub and bladesintegral fulfills the demand above pointed out, the construction of sucha propeller in and of itself presents a problem which heretofore hasbeen unsolved and which has prevented the manufacture'of such a unitarymolded propeller. The molding of a propeller with the hub and bladesintegral has heretofore proved unsuccessful because the hub and theblades required different curing times, so that if the hub was properlycured, the blades were over-cured, and, conversely, if the blades wereproperly cured the hub was under-cured. It is a fllrther object of theinvention, therefore, to provide a molded propeller of plasticcomposition having its hub and blades of such propor tion and design asto permit curing thereof in substantially the same time, 'yet providethe necessary strength and rigidity.

Another object of theinvention is to provide a moldedv propeller havinga hub made hollow to reduce the maximum thickness thereof to correspondto themaximum thickness of the blades.

and rigidity and suiiicient surface for attachment of the blades to thehub.

Still another object is to provide a propeller of molded plasticcomposition having a hub with a generally conical shell and bladeshaving a broad base extending spirally, about the hub substantially thefull axial width of the hub.

Furthermore, considerable difficulty, and consequently expense, isencountered in balancing a propeller so that it will rotate in truebalance on a fan structure. Due to the non-uniformity of a cast metalpropeller, this difficulty is increased materially. 1

Another object, therefore, is to perfect a propeller that may be easilyand economically manufactured'so that it is substantially identical ineach of a desired number of devices, and which in unfinished form issubstantially in true balance, thus reducing to a minimum the time andlabor spent in placing the finished product in drawing, in which:

Fig. 1 is a front face elevational view of a propeller embodying thefeatures of our invention.

Fig. 2 is an edge elevational view of a portion of the propeller shownin Fig. 1, the view bein taken along the line and in the direction ofthe arrows indicated by 2--2 in Fig; l.

Fig. 3 is a rear elevational view of the portion A of the propellershown in Fig. 2. l

Fig. 4 is a sectional view taken along the line 4-4 of Fig. 1.

Fig. 5 is a diametrical, sectional view of the hub of the propellertaken alongthe line 5-5 of Fig. 1.

Whilethe invention is susceptible of various modifications andalternative constructions, it is for purposes of disclosure shown'in thedrawing and will hereinafter be described in, detail in a preferredembodiment butit is not intended that the invention is to be limitedthereby to the specific construction disclosed, but it is intended tocover all modifications and, alternative constructions falling withinthe spirit and scope of the invention as defined in the appended claims.

, The propeller shownin'the drawing; comprises a hub generallydesignated l0 and blades there shown as being merely two innumbenalthough it is understood, of course, that more blades might beemployed, .or that :afpropeller might'beprovided simplywith but a singleblade, a coun A as hereinafter described, the specific shape per se ofthe blades forms no part of the invention.

Suflice it to say, therefore, that for the most part the blades are of agenerally conventional contour, such as found in propellers of the screwtype, capable upon rotation of the propeller emciently to displacefluid.

In order that the propeller disclosed and claimed herein may not besubject to corrosion and rapid deterioration, all of its parts, that is,its hub ID as well as its blades H, are, formed from a moldable plasticcomposition, such as Bakelite," or other resinous condensation product.Further, in order that the propeller may have-a sturdy and rigidconstruction and at the same time be capable of economical manufacture,the propeller is made unitary, that is, with the blades H moldedintegrally with the hub l0. Such a propeller, while fulfilling thedemand for an all composition yet sturdy and economically manufacturedpropeller, in itself presented a major manufacturing problem. -Attemptshave previously been made to solve this problem but without success dueto the difference in time required to cure the hub I and that requiredto cure the blades H. With such a time differential existing, when thehub was properly cured the blades were over-cured, and conversely whenthe blades were properly cured the hub was under-cured, with resultantstructural defects.

To the end that the propeller herein disclosed may be molded as anintegral unit, the hub l0 and the blades H, at their base, are given aunique design and construction resulting in a curing time for the placeof maximum thickness on the hub I0 substantially equal to the curingtime for the place of maximum thickness on the blades II, and at thesame time providing a construction having the necessary strength andrigidity. Accordingly, the hub I0 comprises a shell l2, having generallythe shape of a frustum of a cone, providing a surface to which theblades l I are attached, and a tubular member 0! boss l3 extendingaxially within the shell to provide a bearing for a shaft on which thepropeller is to be mounted. The tubular boss i3 is integral 'at one endwith the small or apex end of the shell l2 and extends rearwardly, inspaced relation to the shell, just short of the end of the shell toprovide a bearing of substantial widthl As best seen in Figs. 3 and 5,added strength may be obtained by means of a plurality of radial webs l4connecting the boss l3 and the shell l2, though such webs are notessential. The hub is completed by a set screw I5 for non-rotatablysecuring the hub onto a shaft received. in the tubular boss l3. It isintended that the shaft be received directly in the tubular boss l3, ametallic sleeve or bushing having been found unnecessary and possiblyeven undesirable.

It can readily be seen. particularly from a consideration of Figs. 4 and5, that with this hollow construction of the hub H] the maximumthickness thereof compares favorably with the maximum thickness of theblades. Thus, the hub and the blades will require substantially thesame; curing time and thus may be molded intesrally. -Such integralmoldingof the blades ll and the hub ID in and of itself gives strengthand rigidity not obtainable in a non-integral construction.

While the maintaining of a substantially equal curing time for moldingof the hub and the blade is the principal and important factor in themanufacture of the propeller, it has been found that slight variationsin the maximum thickness factor may be made and still equality ofstructural strength may be obtained provided compensating changes aremade. For instance, if the diameter of the hub shell I2 is increased andyet the wall thickness of the shell decreased slightly, the structuralstrength of the hub and the blade will still be substantially the samealthough the hub wall is slightly over cured. Conversely, a slightdecrease in hub shell diameter and a corresponding increase in Wallthickness will provide the desired structural strength for the hub eventhough slightly under cured with reference to the blade, and thestructural strength of hub and blade is still, substantially equal. I

It is for the purpose of further increasing the strength and rigidity ofthe propeller that the hub I 0 is made hollow and conical, for by suchconstruction an unusually large surface is provided to which the bladell may be anchored.

- Herein, advantage is taken of this large anchoring surface by formingeach blade II with a wide base l6 (see Figs. 1 and 4) that spirals aboutthe shell l2 of the hub. The base N3 of each blade ll extends the fulldistance from face to face of the shell I2 (see Figs. 1, 2 and 4) andbecause of the spiral mounting has an actual anchorage with the shellthat is greater than the width of the shell.

It is believed apparent from the foregoing that we have not onlyprovided a propelle having many unique and improved features; but onewhich fulfills a long felt want and which solves a problem heretoforeunsolved by those skilled in the art. Strength and rigidity, as well aseconomy in manufacture, are obtained by molding the hub and the bladesof the propeller integrally. Such integral molding of the hub andtheblades has now been made possible by the uniqu design and constructionof our propeller in which the curing time of the hub and the blades issubstantiall equal. By making the hub with an outer shell spaced fromthe portion providing a bearing for a shaft on which the propeller is tobe mounted, sufficient strength could be built into the hub andsufficient area for the anchoring of the blades could be provided, whileat the same time the thickness of any one portion of the hub could besubstantially reduced and conformed to the maximum thickness of theblades. Also with the propeller thus molded as an integral and unitary,structure, the dies may be made so accurate that the unfinishedpropeller as taken from the dies is very nearly in true balance andrequires very little, if any, balancing, thus further reducing the costof manufacture of the finished product.

We claim as our invention:

1. A unitary propeller of a moldable resinous material requiring curingduring the molding thereof, said propeller comprising a hub and bladesextending therefrom, the hub diameter being large in comparison to thethickness of the blades, said hub being hollow so that the shortest paththrough any part of the entire propeller material is of the same orderof thickness as the shortest path through any other part ofthe entirepropeller material whereby substantially uniform overall curing of theentire propeller material will result, said hub having a centrallydisposed boss with a shaft receiving channel, said shaft receivingchannel having a diameter small in comparison to the -hub diameter, saidboss having a plurality of webs extending radially to the hub interior.

2. A unitary propeller of a moldable resinous material requiring curingduring the molding thereof, said propeller comprising a hub and bladesextending therefrom, the hub diameter being large in comparison to thethickness of the blades, said hub being hollow so that the shortest paththrough any part of the entire propeller material is of the same orderof thickness as the shortest path through any other part of the entirepropeller material whereby substantially uniform overall curing of theentire propeller material will result, said hub having a generallyconical shape and wherein the hubs interior is provided with a bosshaving a shaft receiving channel with the diameter of the channel smallin comparison with the hub diameter and wherein a plurality of websextend between said boss and the hub interior.

ROBERT W. DEVORE.

BEN H. YOUNG.

